Error: System.Net.WebException: The operation has timed out on Ftp Web Request Response

This is my code to check Ftp server contains a directory or not. it works fine for the very 1st time. when I execute the second time it throws an exception like "the operation has timed out."

 FtpWebRequest reqt = (FtpWebRequest)WebRequest.Create(destDirPath);
            reqt.Credentials = new NetworkCredential(username, password);
            //reqt.Method = WebRequestMethods.Ftp.ListDirectory;
            // FtpWebResponse respons = (FtpWebResponse)reqt.;
            try
            {
                reqt.Method = WebRequestMethods.Ftp.ListDirectory;
                 FtpWebResponse rps = (FtpWebResponse)reqt.GetResponse();
                return true;
            }
            catch (WebException ex)
            {
                FtpWebResponse response = (FtpWebResponse)ex.Response;
                if (response.StatusCode == FtpStatusCode.ActionNotTakenFileUnavailable)
                {
                    return false;
                }
                return true;
            }
            finally
            {
                reqt = null;
            }

Kindly Help